The end theme song to Gall Force is called Ryote Ippai no Johnny or Johnny Has His Hands Full and is sung by Kahoru Kahirumaki who, at the time, was an idol singer. My guess is that her song was put into there to as to promote her burgeoning career.

As a side note, the only other song she's ever had in anime was the first opening song to the original City Hunter series, which, I believe came out that same here if not one year later, called CITY HUNTER~Ai yo kienaide (an excellent song that captures the feeling of City Hunter perfectly).

I was searching around and I found out that Kahirumaki is still around today and still doing stuff. She's currently known as Kohhy and here is her official site. The song itself was on her album No Problem which has it's site here. There are music samples, but, unfortunately, the don't seem to work.

Just a side note anyway.

I think she speaks English fluently, I wonder what she'd think that some foreigners still remember her song in that show?